/****************************************************************************
 *
 * Copyright 2016 Samsung Electronics All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
 * either express or implied. See the License for the specific
 * language governing permissions and limitations under the License.
 *
 ****************************************************************************/

/****************************************************************************
 * libc/string/lib_memset.c
 *
 *   Copyright (C) 2007, 2011 Gregory Nutt. All rights reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <tinyara/config.h>

#include <sys/types.h>

#include <stdint.h>
#include <string.h>
#include <assert.h>

/****************************************************************************
 * Pre-processor Definitions
 ****************************************************************************/

/* Can't support CONFIG_MEMSET_64BIT if the platform does not have 64-bit
 * integer types.
 */

#ifndef CONFIG_HAVE_LONG_LONG
#undef CONFIG_MEMSET_64BIT
#endif

/****************************************************************************
 * Global Functions
 ****************************************************************************/

#ifndef CONFIG_ARCH_MEMSET
void *memset(void *s, int c, size_t n)
{
#ifdef CONFIG_MEMSET_OPTSPEED
	/* This version is optimized for speed (you could do better
	 * still by exploiting processor caching or memory burst
	 * knowledge.)
	 */

	uintptr_t addr = (uintptr_t)s;
	uint16_t val16 = ((uint16_t)c << 8) | (uint16_t)c;
	uint32_t val32 = ((uint32_t)val16 << 16) | (uint32_t)val16;
#ifdef CONFIG_MEMSET_64BIT
	uint64_t val64 = ((uint64_t)val32 << 32) | (uint64_t)val32;
#endif

	/* Make sure that there is something to be cleared */

	if (n > 0) {
		/* Align to a 16-bit boundary */

		if ((addr & 1) != 0) {
			*(uint8_t *)addr = (uint8_t)c;
			addr += 1;
			n -= 1;
		}

		/* Check if there are at least 16-bits left to be written */

		if (n >= 2) {
			/* Align to a 32-bit boundary (we know that the destination
			 * address is already aligned to at least a 16-bit boundary).
			 */

			if ((addr & 3) != 0) {
				*(uint16_t *)addr = val16;
				addr += 2;
				n -= 2;
			}
#ifndef CONFIG_MEMSET_64BIT
			/* Loop while there are at least 32-bits left to be written */

			while (n >= 4) {
				*(uint32_t *)addr = val32;
				addr += 4;
				n -= 4;
			}
#else
			/* Check if there are at least 32-bits left to be written */

			if (n >= 4) {
				/* Align to a 64-bit boundary (we know that the destination
				 * address is already aligned to at least a 32-bit boundary).
				 */

				if ((addr & 7) != 0) {
					*(uint32_t *)addr = val32;
					addr += 4;
					n -= 4;
				}

				/* Loop while there are at least 64-bits left to be written */

				while (n >= 8) {
					*(uint64_t *)addr = val64;
					addr += 8;
					n -= 8;
				}
			}
#endif
		}
#ifdef CONFIG_MEMSET_64BIT
		/* We may get here with n in the range 0..7.  If n >= 4, then we should
		 * have 64-bit alignment.
		 */

		if (n >= 4) {
			*(uint32_t *)addr = val32;
			addr += 4;
			n -= 4;
		}
#endif

		/* We may get here under the following conditions:
		 *
		 *   n = 0, addr may or may not be aligned
		 *   n = 1, addr is aligned to at least a 16-bit boundary
		 *   n = 2, addr is aligned to a 32-bit boundary
		 *   n = 3, addr is aligned to a 32-bit boundary
		 */

		if (n >= 2) {
			*(uint16_t *)addr = val16;
			addr += 2;
			n -= 2;
		}

		if (n >= 1) {
			*(uint8_t *)addr = (uint8_t)c;
		}
	}
#else
	/* This version is optimized for size */

	unsigned char *p = (unsigned char *)s;
	while (n-- > 0) {
		*p++ = c;
	}
#endif
	return s;
}
#endif
